Regenerative cycle electric incandescent lamp



968 ca. R. T'JAMPENS ETAL 8,

REGENERATIVE CYCLE ELECTRIC INCANDESCENT LAMP Filed June 30, 1965 2Sheets-Sheet 1 INVENTORJ GERMAIN R. T'JAMPENS RIKSTERUS A. J. u. MEIJERMARTINUS H. A. VAN DEWEIM 22M GENT I 24. 1968 s. R. TJAMPENS ETAL 3,,512.

REGENERKTIVE CYCLE ELECTRIC INCANDESCENT LAMP 2 Sheets-Sheet 2 FiledJune 30. 1965 INVENTORJ GEMMIN I. r'unrzns mxsrenus A. J. no. new"MARTINUS ll. VAN DE "END AGENT United States Patent 3,418,512REGENERATIVE CYCLE ELECTRIC INCANDESCENT LAMP Germain Remi TJampens,Riksterus Auguste Johannes Maria Meijer, and Martinus Henricus Adrianusvan de Weijer, Emmasingel, Eindhoven, Netherlands, assignors to NorthAmerican Philips Company, Inc., New York, N.Y., a corporation ofDelaware Filed June 30, 1965, Ser. No. 468,482 Claims priority,application Netherlands, July 1, 1964, 6407446; July 16, 1964, 6408084 5Claims. (Cl. 313185) ABSTRACT OF THE DISCLOSURE An incandescent lamphaving a tungsten filament surrounded by a light pervious envelope whichutilizes certain of the hydrogen halides or chlorinated or brominatedhydrocarbons to maintain a transport cycle between the tungsten filamentand the inner Wall of the envelope.

The invention relates to an electric incandescent lamp in which atungsten filament is arranged in a bulb which is pervious to light. Thebulb contains, in addition to an inert filling gas, a reactive transportgas the object of which is to prevent blackening of the bulb duringburning by means of a regenerative cyclic process in which the tungstenwhich evaporates from the filament is converted into a volatile compoundwhich decomposes in the proximity of or on the filament. In such a lampthe wall of the bulb is not blackened and the filament experiences noloss of weight. A tungsten filament is understood to include wires orcoiled wires of tungsten.

The basic idea of a regenerative cycle to prevent blackening of the bulbof an incandescent lamp is already rather old. For example, a lamp hasalready been described which contains chlorine, bromine, or iodine as atransport gas and in which such a regenerative cycle was said to takeplace. However, in said lamp all metal components other than thefilament, for example, supports and current supply wires and thecomparatively cold ends of the filament had to be protected against theaggressive transport gas. In practice the protection of the said colderparts of the filament and of the other metal parts has proved to be asubstantially insurmountable difficulty.

From later experiments it has appeared that a considerable improvementcan be obtained when the geometry of such a lamp is chosen to be suchthat during burning of the lamp the comparatively cold ends of thefilament and other comparatively cold tungsten parts in the lamp assumea temperature at which the said parts are not or only slightly attackedby the reactive transport gas.

When using iodine as the transport gas this requirement can rathereasily be fulfilled structurally. When using iodine the construction ofthe lamp must be such that the comparatively cold parts of tungstenduring burning assume a temperature above approximately 800 C. and thewall of the bulb assumes a temperature above approximately 250 C. Thiscan be realized with a cylindrical bulb of quartz in which a filament oftungsten is arranged along the axis of the cylinder. Such a lamp has agreater efiiciency expressed in lumen/watt than normal incandescentlamps have, while maintaining a substantially constant lumen/Watt outputduring the whole life of the lamp. In these types of lamps, as is thecase in normal lamps, the filament fuses at a comparatively hot point.

When iodine is replaced by chlorine or bromine which chemically are moreactive than iodine under otherwise the same conditions, attack of thecomparatively cold tungsten parts in the lamp occurs to a greaterextent. In

this case, tungsten crystals in the form of dendrites are formed at theends of the filament, at the points Where the filament is supported, andat, the comparatively cold regions along the filament. In order toprevent attack by the transport gas the temperature of the entirefilament in the presence of chlorine would have to be at leastapproximately. 2500" C., and in the presence of bromine at leastapproximately 1700 C. during burning. Structurally this is difiicult torealize with the present materials known for lamp manufacture.

The use of iodine as the transport gas provides many drawbacks. Forexample, it is difiicult to introduce the exact quantity of iodinerequired in a lamp. The vapor pressure of iodine at room temperature islower than the pressure required in the lamp for a proper functioning ofthe tungsten-iodine cycle. The filling is consequently performed usuallyat temperatures higher than room temperature. In that case it isnecessary to accurately control the temperature of the filling deviceand of the lamp during filling. In addition, iodine is very reactivewith respect to many metals; consequently the iodine filling device mustconsist of iodine-resistant material.

The tungsten-iodine cycle has been found tobe particularly sensitive toall kinds of impurities. This sensitivity requires that all thematerials used for the lamp have to be subjected to an extensivecleaning process. This is particularly true in the case of the tungstenfilament.

The colour of iodine is undesired in certaincases, in the visible lightan absorption of 4 to 5% occurs.

In order to mitigate the dosing difficulties it has already beenproposed to fill lamps with hydrogen iodide (HI) which at roomtemperature is a gas. Since quartz is considerably permeable to hydrogenalready, at a temperature of 300 C. the hydrogen would disappear fromthe lamp wholly or substantially wholly in the long run during burningof the lamp. The same efl'ect Would occur when the lamp is filled withhydrogen chloride or hydrogen bromide. After some time atungsten-chlorine or tungsten bromine cycle would be obtained which,however, have the disadvantageous properties already described.

It is the object of the invention to mitigate a number of drawbacksassociated with the use of iodine.

According to the invention this may be achieved by an incandescent lamp,comprising a tungsten filament, an envelope means containing saidfilament which has 'a low permeability to hydrogen, an inert filler gaswithin said envelope, and a gaseous mixture within said envelopeselected from the group consisting of hydrogen and chlorine, or hydrogenand bromine.

The dosing of chlorine and hydrogen, and bromine and hydrogen isconsiderably simpler than of iodine, because these elements are gases orare volatile at room temperature or can be dosed via volatile or gaseouscompounds which, in addition, are usually less reactive than iodine.These volatile or gaseous compounds are, for example, hydrogen chlorideand chlorinated hydrocarbons which, in the case of hydrogen chloride indecomposition supplies chlorine and hydrogen, or in the case of thechlorinated hydrocarbons which, in decomposition form, chloroform,methylene chloride, ethylene dichloride, mixtures of these, or ofmethane and carbon tetrachloride. The gaseous compounds hydrogen bromideand brominated hydrocarbons which on decomposition, supply bromine andhydrogen in the case of hydrogen bromide and bromoform, methylenebromide, methyl bromide, ethylene-dibromide, mixtures of these or ofmethane and other hydrocarbons with carbon tetrabromide in the case ofthe brominated hydrocarbons. By suitable choice of chlorinated orbrominated hydrocarbon, if required together with hydrogen chloride orhydrogen bromide respectively and/or chlorine or bromine and/or hydrogena carbon getter may also be introduced into the lamp for getteringoxygen which element may disturb the regenerative cyclic process.

In practice it has been found that the ready functioning of thetungsten-hydrogen-chlorine and of the tungstenhydrogen-bromine cycle isfar less dependent on the purity of the materials from which the lamp ismanufactured than is the case with the tungsten-iodine cycle. During theinvestigation which has resulted in the invention it has been found, forexample, that tungsten filaments could be used with hydrogen chloride orhydrogen bromide 'as the reactive transport gas, which filaments couldnot be used with iodine as the reactive transport gas due to theexistence of impurities, unless the cycle was activated by a smallpercentage of oxygen.

In addition it has been found in these experiments that the use ofhydrogen iodide gives considerably worse results than iodine alone. Thismust be ascribed to the retarding influence of hydrogen on thetungsten-iodine cycle. This'retarding action of hydrogen whichconsequently is not permissible when using iodine, has now been found tobe particularly favourable when using chlorine or bromine. The drawbacksof the tungstenchlorine and of-the tungsten bromine cycle, namely theattack of comparatively cold parts of tungsten in the lamp, issufficiently reduced in the presence of hydrogen. This is probably basedon the fact that hydrogen chloride and hydrogen bromide do not attacksolid tungsten and are not dissociated in hydrogen and chlorine orhydrogen and bromine respectively at the temperature of thecomparatively cold parts of tungsten in the lamp. In a lamp containinghydrogen chloride, at the highest temperature only little hydrogenchloride is dissociated on the filament. The quantity of chlorineoriginating from this dissociation, however, may be sufiicient to causea cycle, by which blackening is prevented, to function when the quantityof hydrogen chloride in the lamp is sufliciently high. On the other handwhen the quantity of hydrogen chloride is too large, blackening mayoccur also. The filling pressure of hydrogen chloride to be chosendepends in a complicated manner upon the temperature of the filamentduring burning of the lamp, on the geometry of the lamp and the fillingpressure of the inert gas. However, for each type of lamp, the mostfavourable filling pressure of hydrogen chloride can be determined bysimple experiment. However, it has been found that a favourable fillingpressure usually lies between 7 and 14 mm. with respect to hydrogenchloride.

The reactive transport gas comprising hydrogen and chlorine need notcontain accurately equivalent quantities of chlorine and hydrogenalthough this is to be preferred. A small excess of hydrogen may befavourable in certain conditions, while a small excess of chlorine neednot have a disturbing influence. The best results are obtained when theratio in gram atoms between chlorine and hydrogen in the gas mixtureslies between 4:5 and 5:4.

From the experiments which resulted in the invention it has been found,that optimum results may be obtained when at the beginning of life thelamp contains per cm. of bulb capacity between 0.35 and 100x10 gramatoms of hydrogen between and 0.35 10- and 1.00 X l0 of chlorine as suchor in the form of a compound, for example, HCl or a chlorinatedhydrocarbon.

In order to lose no tungsten by condensation of tungsten chlorides onthe wall of the bulb, iti s to be preferred to construct the lamp sothat the wall of the bulb during burning reaches a temperature ofapproximately 350 C. or higher. Structurally, this can easily berealized. Since no blackening of the bulb occurs by condensation oftungsten on the wall of the bulb the distance between the filament andthe wall of the bulb may be chosen to be very small.

In spite of the fact that the comparatively cold tungsten parts aresubstantially not attacked by hydrogen bromide,

it has surprisingly been found that the wall of the bulb of a lampcontaining hydrogen bromide remains transparent. It has been found inaddition that a lamp, the wall of the bulb of which is blackened bytungsten deposition, becomes entirely bright after having been filledwith HBr or a HBr-supplying substance or mixture of substances after ashort period of burning. The filling pressure of hydrogen bromide to bechosen depends upon the temperature of the filament during burning ofthe lamp, upon the geometry of the lamp and the filling pressure of theinert gas. However, the most favourable filling pressure of hydrogenbromide can be determined for each type of lamp with a restricted seriesof simple experiments. It has been found that this filling pressure isof minor eriticalness and may lie between 1 mm. and 1 atm. HBr.

The reactive transport gas preferably contains nonequivalent quantitiesof bromine and hydrogen. An excess of hydrogen has been found to be veryfavourable for the life of the lamp. The best results are obtained whenthe ratio in gram atoms between bromine and hydrogen in the gas mixturelies between 1:1 and 1:7, although ratios to 1:10 and higher may givegood results also; however, the absolute quantity of hydrogen may notbecome so high that the heat conductivity of the filling gas becomes toogreat as a result.

From the experiments which resulted in the invention, it has also beenfound that optimum results are obtained when at the beginning of lifethe lamp contains per cm. of bulb capacity between 1.5 X 10- and 1.05 X10- gram atoms of hydrogen and 1.5 l0- and 1.5 10" gram atoms of bromineas such or in the form of a compound as HBr or a brominated hydrocarbon,if required together with hydrogen and/ or bromine.

In order to lose no tungsten by condensation of tungsten bromides on thewall of the bulb it is recommendable to construct the lamp so that thewall of the bulb during burning reaches a temperature of approximately300 C. or higher. structurally, this can be simply realized. Since noblackening of the wall occurs by condensation of tungsten on the wall ofthe bulb the distance between the filament and the wall of the bulb maybe chosen to be very small.

Various measures, also in combination, may be used to prevent the lossof hydrogen which is detrimental to the life of the lamps whichaccording to the invention contain hydrogen and a halogen chosen fromthe group consisting of chlorine and bromine.

(A) The lamp may be constructed so that during operation of the lamp atthe voltage for which the lamp is designed the temperature of thefilament is so high that the resulting life of the filament is alreadyended before the comparatively cold tungsten parts in the lamp aredamaged as a result of chemical attack by chlorine or bromine in amanner which is detrimental to the life of the lamp. Such lamps may beused in optical systems in which it is not so much the long life of thelamp but rather the maintenance of a substantially constant luminousefiiciency per watt during the whole life of the lamp that matters.Examples hereof are, for example, projection lamps, film lamps andphotographic lamps, motorcar lamps and lamps for other special uses inwhich the filament temperature in general exceeds 3000 K. and theguaranteed life of the lamp usually is 15 to hours. It has been found tobe very readily possible however to manufacture lamps comprisinghydrogen and bromine having life-times of 1000 hours and more.

(B) The bulb may also be manufactured from a type of quartz which isless permeable to hydrogen than is melted silicon dioxide.Alternatively, high-melting-point types of glass which do not passhydrogen could be used.

(C) The bulb of a material which passes hydrogen may be provided in abulb which does not pass hydrogen and the space between the two bulbsmay be filled with hydrogen gas or a mixture of hydrogen and an inertgas.

(D) To maintain the desired ratio of hydrogen and chlorine or bromineduring the whole life of the lamp substances may be placed in the lampwhich either can replace the hydrogen which is diffused away in andpossibly through the wall of the bulb by supplying hydrogen or can bindthe excess of chlorine or bromine which is formed as a result of thediffusing away of hydrogen or which combine those two functions.Alternatively, mixtures of substances showing one of those functions maybe used.

A further advantage is that the hydrogen-chlorine and hydrogen-brominecompounds in question substantially always are colourless and thatconsequently no loss of light occurs by absorption.

In order that the invention may readily be carried into effect, it willnow be described in greater detail, by way of example, with reference tothe accompanying figures in which:

FIG. 1 is a cross-section of an incandescent lamp comprising an innerbulb and an outer bulb wherein the filament is arranged in the innerbulb and a hydrogencontaining gas is present between the inner bulb andthe outer bulb, and

FIGS. 2 and 3 are also cross-sections of incandescent lamps.

FIG. 1 shows a partial cross-section of a filament lamp. A coiledfilament :1 of tungsten which is connected to molybdenum plates 2 isarranged in a cylindrical bulb 3 of quartz. The filament is supported bythe coiled tungsten supports 7 and 8. By means of the metal holders 4and 5, which also serve as current conductors to the filament 1. Thelamp is fixed in an outer bulb 6 of glass or another transparent andgas-tight material. The inner bulb contains a mixture of an inert gasand hydrogen chloride, the intermediate space between the inner bulb andthe outer bulb contains a hydrogen-containing inert gas. In oneembodiment the inner bulb had an inside diameter of 7 /2 mm., a lengthof 150 mm., and the coiled tungsten filament has a length ofapproximately 150 cm. and a diameter of 1 mm. The filament had 225 v.applied thereto for a 1000 watt output with a luminous efficiency of 20lumen/watt. The inner bulb was filled with a mixture of argon andhydrogen chloride which contained 1.6% by volume of hydrogen chloride(partial pressure hydrogen chloride 11.2 mm.) to a pressure of 700 mm.The space between the inner bulb and the outer bulb was filled to apressure of 200 mm. with a mixture of argon and hydrogen of which thehydrogen content was varied between and 1.0 Torr (00.5% by volume)according to Table 1 below which shows the life of the lamp inaccordance with this percentage of hydrogen.

In none of the cases in which hydrogen was present in the outer bulb didattack of the supports occur which indicates that no detrimentalquantity of hydrogen is lost during the burning time stated. In theabsence of hydrogen in the outer bulb, the supports were rapidlyattacked. The lamps burned in a horizontal position.

In the following experiments the load of the filament was chosen to beso that the life thereof was shorter than the time at which a variationof the chlorine-hydrogen ratio by loss of hydrogen occurred which wasdetrimental to the life.

FIG. 2 shows a cross-section of a so-called photographic lamp of 1000watt, 3400 K. colour temperature at 225 volts and 32 lumen/watt luminousefficiency. The lamp comprises a bulb 3 of quartz having the followingdimensions: inside diameter 7.5 mm., length 89 mm.,

coiled tungsten filament 1:1 length 1.32 m., diameter of the wire 172length of the coil 85 mm. Reference characters 7 and 8 indicatesupports, and 2 indicates a molybdenum plate. The lamps were filled witha mixture of argonnitrogen (8%) and 1.6% by volume of HCl, fillingpressure 700 mm. The life was the same as that of an iodine lamp whichcontained mm. of I and was approximately 40 hours. The same was foundwhen methylene dichloride was used with a filling pressure of 9 mm. Thelamps were filled with a mixture of argon-nitrogen (8%) at a fillingpressure of 600 mm. and varying quantities of bromine containingtransport gas according to Table 2. The average life of comparableiodine lamps is approximately 27 hours.

TABLE 2 Filling gas Filling pressure 1111 mm.

5.3 5.6 6.1 7. 5 l0. 9 24. 6 5.3 5.3 5.3 5.3 5.3 5.3 40 40 40 4.0 r 710.5 14 21 28 Average life in hours In all the cases between 30 andhours a 1 Average life in hours.. 30

Experiments were also performed with so-called projection lamps,capacity approximately 1 cm. luminous efliciency 30 Im./ watt at 100watt and 12 volt. The life of comparable iodine lamp on an averagehours.

When filled with 4 atm. of krypton and quantities of HBr between 7 and23 mm. an average life of hours was found in all the cases.

FIG. 3 shows a partial cross-section of a filament lamp. A coiledfilament 1 of tungsten which is connected to molybdenum plates 2 islocated in a cylindrical bulb 3 of quartz. The filament is supported bythe coiled supports 7 and 8 of tungsten. The lamp contains a mixture ofan inert gas and hydrogen bromide or a compound supplying hydrogenbromide. The proportions of the bulb were: inside diameter 7.5 mm. andlength mm. The coiled tungsten filament had a length of approximately150 cm., and a wire diameter of 1 mm. 225 Volts were applied thereto todevelop a 1000 watt output. The resulting luminous efiiciency was 22lumen per watt. The bulb was filled with a mixture of argon and hydrogenbromide to a pressure of 3 atm. After burning for 600 hours lamps whichcontained 7 and 14 mm. of HBr respectively had not yet fused and thesupports were not yet attacked.

In this and the foregoing experiments the load of the filament waschosen to be so that the life thereof was shorter than the time in whicha variation of the brominehydrogen ratio which is detrimental to thelife occurred by loss of hydrogen.

What is claimed is:

1. An incandescent lamp comprising an envelope means of low permeabilityto hydrogen; a tungsten filament within said envelope, an inert filler\gas disposed within said envelope, and a gaseous mixture disposedwithin said envelope selected from the group consisting of hydrogen andchlorine, hydrogen and bromine, chlorinated hydrocarbons and brominated'hydrocarbons, wherein said envelope comprises a quartz glass bulbcontaining said filament, and an outer globe surrounding said bulb inspaced relation, said globe comprising a material permeable to light andhaving low permeability to hydrogen, and the space between said bulb andglobe having a hydrogen filler, and means supporting said bulb withinsaid globe.

2. An incandescent lamp comprising a substantially cylindrical envelopehaving a lower permeability to hydrogen than melted silicon dioxide; acoiled tungsten filament within said envelope having a linear axissubstantially coincident with the centroidal axis of said cylindricalenvelope, said envelope closely surrounding said filament so that theinterior wall of said envelope is heated during operation to atemperature in excess of 300 C.; an inert gas disposed within saidenvelope and a gaseous mixture disposed within said envelope forinitiating and maintaining a regenerative cycle wherein the tungstenfrom the filament is vaporized, deposited on said inner envelope wall,combined with said gaseous mixture, returned to the region of the heatedfilament, separated from said gaseous mixture and redeposited on saidfilament, said gaseous mixture being selected from the group consistingof hydrogen chloride and the chlorinated hydrocarbons, wherein saidgaseous mixture within said envelope is at a partial pressure within therange of 7 to 14 mm. and the ratio in gram atoms between chlorine andhydrogen is in the range between 4:5 and 5:4.

3. An incandescent lamp according to claim 2 wherein the number of gramatoms of hydrogen is within the range of 0.35 10 to 1.00 10 and thenumber of gram atoms of chlorine is within the range of 0.35 X10 to 1.0010 per cubic centimeter of envelope volume.

4. An incandescent lamp comprising a substantially cylindrical envelopehaving a lower permeability to hydrogen than melted silicon dioxide, acoiled tungsten fila-,

tungsten from the filament is vaporized, deposited on said innerenvelope wall, combined with said gaseous mixture, returned to theregion of the heated filament, separated from said gaseous mixture andredeposited on said filament, said gaseous mixture being selected fromthe group consisting of hydrogen bromide and the brominatedhydrocarbons, wherein said gaseous mixture within said envelope is at apartial pressure within the range of 1 m-m. to 1 atmosphere and theratio in gram atoms between bromine and hydrogen is in the range between1:1 and 1:7.

5. An incandescent lamp according to claim 4 wherein the number of gramatoms of hydrogen is within the range of l.5 10 and 1.05 10 and thenumber of gram atoms of chlorine is within the range of 15x10" and 1.5 x10 per cubic centimeter of envelope volume.

References Cited UNITED STATES PATENTS 1,655,488 1/1928 Wolff et al.313222 3,022,438 2/1962 Cooper 3l3--222 3,091,718 5/1963 Shurgan 313222JAMES W. LAWRENCE, Primary Examiner.

P. C. DEMEO, Assistant Examiner.

US. Cl. X.R.

Patent No. 3,418,512 Dated December 24, 1968 lnventofls) GERMAIN R. TJAMPENS ET AL It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 15, cancel "chlorine" and insert bromine Signed andsealed this 5th day January 19 71 Anew u. Jr. mm s. .m. was offiGomiasiom of Patents

